We have developed an observable sensitive fiber nonlinear polarization sensing method based on the whispering gallery
mode (WGM). The spectral position of the WGM excited by evanescence field shifts in response to the refractive index
change of the fiber’s dielectric caused by nonlinear polarization interaction with incident light field or surrounded
electromagnetic filed. Theoretical resonance spectral shift equation was derived and calculation showed that a sensitivity
of approximately 0.0172∼0.0196 RIU (refractive index unit) per nm at least was achieved due to the extremely high Q
factor associated with the WGM.